The present invention relates to a fragmentation processing device and in particular, to a fragmentation processing device for, in the case of accommodating various lines to transfer IP packets, performing a fragmentation process at high speed only with hardware and a fragmentation processing apparatus implementing thereof.
In general, a router and the like on an IP network has a fixed size of a packet to be sent and received according to specifications of an accommodated link layer protocol. Here, a size of an IP packet sendable on the sending side is called an MTU (Maximum Transfer Unit) size and a size of an IP packet receivable on the receiving side is called an MRU (Maximum Receive Unit) size.
These MTU size and MRU size can have different values set for an input line and an output line respectively. Thereby there are cases where an apparatus on the IP network such as a router has to execute a fragmentation process. That is, a fragmentation process is required in the case where an IP packet of a size larger than the MTU size has to be sent. For instance, in the case of sending an IP packet of IP packet length A to the output line of which MTU size is B (A>B), the router cannot send this IP packet without dividing it into a size B or smaller. In this case, a fragmentation process is executed and an IP packet of the above size A is divided into IP packets of the MTU size or smaller and then sent. As for this fragmentation process, there is a process described in IETF RFC1812 Requirements for IP version 4 Routers, for instance.
However, this fragmentation process is not a process executed on every router or the like, in spite of the router or the like has a function of fragmentation process in general. To be more specific, it may not be required in the case where routes are designed so that the MTU size coincides with the MRU size. For that reason, the fragmentation process has been conventionally executed by software.
There are a variety of physical line types existing currently, and each of them has a different MRU size. For this reason, the fragmentation process is frequently executed when transferring IP packets between different physical lines. In this case, as the fragmentation process is executed by software as aforementioned, there is a problem pointed out that an IP packet transfer process takes a lot of time.
In addition, there is an another problem that, as the conventional fragmentation process by software is executed after receiving the entire IP packets, the time for starting the fragmentation process delays in the case of receiving long IP packets so that the IP packet transfer process takes a lot of time.
To solve these problems, Japanese Patent Laid-Open No. Hei 11-168492 discloses a conventional technology on a router apparatus implementing a function of examining the minimum MTU size of a route on which the IP packets are transferred on an IP network.
However, the route on which the IP packets are transferred can be different depending on a state of this network, and so it is not always one. Thus, in the case where the IP packets are transferred to a route different from the examined route, the fragmentation process executes on the network.
In addition, all the router apparatuses or the like are required to implement the above technology.
The present invention has been achieved considering the above problems, and its object is to provide a fragmentation processing device. In addition, another object is to provide a fragmentation processing apparatus such as a router implementing a fragmentation processing device.